1. Field of the Invention
The present invention relates to a high-frequency switch module including a switch IC that is mounted on a multilayer board.
2. Description of the Related Art
High-frequency switch modules are used in front end portions of mobile phones and other suitable devices. A high-frequency switch module includes a multilayer board and a switch IC mounted thereon. The switch IC connects a selected terminal selected from among a plurality of terminals to a shared terminal. The multilayer board includes surface electrodes connected to terminals of the switch IC, mounting electrodes, and internal electrodes.
In a high-frequency switch module, power noise generated in the outside or in the switch IC may be superimposed on an internal wiring (power supply wiring) for supplying power to the switch IC. A problem arises when the power noise leaks to an internal wiring other than the power supply wiring in the multilayer board. In particular, if the power noise leaks to an internal wiring (transmission wiring) for transmitting a transmission signal when the switch IC is powered on, there is a possibility that a property degradation, such as harmonic distortion, will occur, which is a serious problem.
Therefore, in order to solve this problem, a configuration may be used in which a power supply wiring is sandwiched between internal ground electrodes (see, for example, Japanese Unexamined Patent Application Publication No. 2001-53449).
In Japanese Unexamined Patent Application Publication No. 2001-53449, an internal ground electrode for preventing power noise superimposed on a power supply wiring from leaking to another internal wiring is provided on an entire predetermined interface within a multilayer board. Thus, since the internal wiring other than the power supply wiring, a circuit element, or other wiring faces the internal ground electrode, a desired impedance or electrical property may not be obtained. In addition, power noise may leak from the power supply wiring through the internal ground electrode to the other internal wiring.